GB2191154A - A submersible transport vessel - Google Patents

Abstract

A submersible transport vessel comprises a deck construction (2) especially for carrying heavy and bulky loads (7), said deck construction being connected to at least one lower pontoon (1) spaced below the deck construction by means of a plurality of connection columns (3, 5) with a stabilizing function. At least one stabilizer box (4) projects above said deck construction and the transport vessel is submersible from a level (9, Figure 4) at which only a part of said lower pontoon lies below the water surface down to a level (10, Figure 4) at which said lower pontoon lies entirely below and said deck construction entirely above the water surface, and down to a level (8, Figure 4) at which said lower pontoon and said deck construction are situated entirely below the water level and only the upper part of at least one stabilizer box projection above said deck construction projects above the water level. Preferably, the deck construction is constructed as a supporting surface for taking up a conventional transport pontoon (6). <IMAGE>

Description

SPECIFICATION A submersible transport vessel This invention relates to a submersible heavy-duty transport vessel comprising a deck construction for carrying in particular heavy and bulky loads and being submersible down to a level at which said deck construction is underwater.

Asimilartransportvessel is used in particularfor transporting heavy and bulky constructions by sea towards or from a location at sea where such constructions are to be installed ortaken up by means of e.g. a floating crane from e.g.asupporting construction anchored in the sea bottom for the purpose of mounting or demounting a working plafform orthe like. Loading or unloading a construction ashore nearthe construction or repair site can take place, if it has sufficient buoyancy, by lowering the vessel uniti the construction is buoyant and be towed away. In the eventthatthe construction has insufficient buoyancy, it should be pushed from ashore directly onto thetransport vessel, which imposes restrictions on the places where this can be done, since the transport vessel has to be lowered for that purpose until the deck is at shore level.

With such a mode of operation, further problems may occur when a construction is taken up from, or placed on, the transport vessel by means of a floating crane due to the undulation ofthe sea surface. With the present transport means the I imit for mari ne operations is about 1.5 m ofsignificantwave height.

The present generation of floating cranes can often operate even at 3-3.5 m ofsignificantwave height, so that the progress of the operations can stagnate due to the inability of the transport means to be used in the lifting operations, whilethe floating crane, in actual fact, could continue its operations. Thus, only the transport means cause the loss of highly valuable time.

It is an object of the present invention to provide a submersible transport vessel of the above described type constructed in such a mannerthat its can be used, independently of the water depth, nearthe construction or repair site ashore and, moreover, can be rendered so insensitive to wave motion that it is no longerthe only cause of stagnation ofthe construction operations at sea.

This is achieved, according to the present invention, in that the deck construction is connected, by means of a plurality of connection components with a stabilizing function, to at least one lower pontoon spaced below the deck construction, with at least one stabilizer box projecting above the deck construction and the transport vessel being submersible from a level atwhich only a partofthe lower pontoon lies below the water surface, down to a level at which the lower pontoon lies entirely below and the deckconstruction entirelyabovethewater surface, and down to a level at which the lower pontoon and the deck construction lies entirely below the water surface and only the upper part of at least one stabilizer box projecting above said deck construction projects above the water surface.These features permit using the transport vessel in the manner of a semi-submersible, i.e. bringing it into a position that is stable and considerably less sensitive to wave motion by submersion to a first level at which the water surface is between the deck construction and the lower pontoon. Just as in the case of a semi-submersible, only a part of the lower pontoon lies below the water surface during sailing so asto create optimum sailing conditions. Finally, with a view to enabling optimum loading and unloading ofthe submersible transport vessel near the shore where the construction is mostly built, repaired and/or maintained, the transport vessel is submersible to the extent that the deck construction comes to lie underwater.In that case, a construction to be transported, if sufficiently buoyant, can be towed away, floating independently, towards or awayfrom the transport vessel from ortowards water of less depth. This presents a highly suitable mannerofloading or unloading a construction near the shore without requiring voluminous lifting gear for placing the construction onto the transport vessel or necessitating ports having deep fairways.

When the construction to be transported has insufficient buoyancy, it is perferable, and in accordance with a further embodiment of the present invention, that the deck construction is constructed as a supporting surface fortaking up a conventional transport pontoon and the stabilizer boxes projecting above the deck construction at the front and/orthe rear ofthe transport vessel are spaced such a distance apart that a transport pontoon to be taken up can sail therebetween.In this manner,theconstruction can be handled nearthe shore on a conventional transport pontoon of slight draught,which pontoon for marine transport is manoevredto a position overthetransportvessel submerged to its lowest position, and is thus lifted together with the construction by unballasting the transportvessel,whilethe unloading ofa pontoon with a construction resting thereon takes place by submerging said transport vessel down to its lowest position, thereby causing the pontoon to float on the water independently.

In accordance with a further embodiment of the present invention, it is preferred that the stabilizer boxes are disposed at least partly on either side at the front and the rear ofthe deck construction and the lower pontoon. There is thus obtained, in top view, a H-shaped construction, enabling the transport vessel to be placed in an optimum position, i.e. abeam of the floating crane and as closely as possible to it, so that the crane can getto the centre of the transport vessel with a relatively short reach, which increases the capacity ofthe crane as regardsthe maximum load itcan lift.

One embodiment of the transport vessel according to the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawing, in which: Figure 1 is a perspective view of a transport vessel accordingtothepresentinventiorl; Figure2 is a top view of Figure 1; Figure 3 shows the transport vessel of Figure 1 with a construction placed on a pontoon and to be transported; and Figure 4 is a front view of Figure 3.

Thetransportvessel shown in Figure 1 comprises a lower pontoon 1, a deck construction 2, stabilizer boxes 3, 4 and connection columns 5. Lower pontoon 1 and deck construction 2 are maintained at a fixed interspace by stabilizer boxes 3 and connection columns 5. The stabilizer boxes are positioned on either side of lower pontoon 1 and deckconstruction 2atthefrontandthe rearofthe transport vessel, so that, as shown in Figure 2, said vessel obtains a H-shape in top view, permitting a floating crane to be broughttowithin a minimum distance when the transport vessel is positioned abeam of the floating crane without being hindered by the stabilizer boxes 3, 4.

Figure 3 showsthetransportvessel of Figure 1 with a conventional transport pontoon 6 positioned thereon, carrying, in its turn, a construction 7 to be transported.

To arrive from the unloaded position shown in Figure 1 to the ioaded position shown in Figure 3,the transportvessel issubmergedto about level 8 indicated in Figure 4, i.e. a level atwhich both lower pontoon 1 and deck construction 2andstabilizer boxes 3 are entirely below the water surface. Above the water surface project only parts of stabilizer boxes 4. In this submerged position, deck construction 2 lies underwaterto the extentthat pontoon 6with construction 7 placed thereon can be sailed ortowedto a position over deck construction 2.After pontoon 6 has been positioned relatively to thetransportvessel,this is again lifted by pumping away ballastwaterthat may be present in the deck construction,the stabilizer boxes, the connection columnsand/orthe lower pontoons. Lifting is effected uptothesailing level shown at9 in Figure 4.

In this position, wherein the underwater drag is minimum, construction 7 is transported to its destination. On arrival at that location,thetransport vessel is submerged down to a level at which the lower pontoon 1 is entirely underwater but the deck construction 2 entirely above the water, i.e., a level as e.g. shown at 10 in Figure 4. In this position,the transport vessel has the least sensitivity to wave motion.

When construction 7 has sufficient buoyancy, the uses of a pontoon 6 can be dispensed with and construction 7 can be supported directly on deck construction 2. Furthermore, it is naturally also possible to handle more than one construction 7, whether or not positioned on one or more pontoons 6.

It is observedthatthetransportvessel can just as well be employed for operations otherthan the transport of constructions towards orawayfrom a marine construction site. For instance, the transport vessel can also be used for all kinds of other transports, such as the transport by sea of loads from one portto another, the transport of heavy and bulky elements to be submerged etc. to a given place. Also, thetransportvessel can be used as a platform for a floating lifting gear normally suitable for in-port use onlyso asto use it also at sea orforotherfloating elements or constructions for providing a platform for these that is less sensitive to wave motion.

It is observed that many modifications and variants are possible within the scope of the present invention. For instance, the arrangement, distribution and design of the stabilizer boxes and connection columns shown in the figures are variable in many ways. The connection columns 5 could be replaced for instance by a single, centrally positioned centre column of larger cross section.

Besides, stabilizer boxes 4 may be connected detachably to stabilizer boxes 3, so that, e.g.for handling construction with very large bottom surfaces, two stabilizers boxes 4 can be uncoupled and possibly be connected to the other stabilizer boxes 4, thereby obtaining a largerflat bearing area.

Instead of one lower pontoon 1 connected to all the stabilizer boxes 3 and connection columns 5, said pontoon can also consists of a plurality of separate elements, such as two longitudinal floats which may be coupled transversely, e.g. by cross bars. All connection columns 5 and stabilizer boxes 3 could also be constructed identically, e.g. as columns of larger cross section than connection columns 5 and of smaller cross section than stabilizer boxes 3.

Depending on the length of the vessel, it is also possible to omit connection columns 5 and to use only stabilizer boxes 3. Possibly, the two stabilizer boxes 3 and/or 4 situated at the front and/or the rear ofthetransportvessel may be replaced by one continuous stabilizer box.

Claims (4)

1. Asubmersibletransport vessel comprising a deck construction especiallyforcarrying heavy and bulky loads and being submersible down to a level at which the deck construction lies underwater, characterized in that said deck construction is connected to at least one lower pontoon spaced below the deck construction by means of a plurality of connection columns with a stabilizing function, at least one stabilizer box projecting above said deck construction and the transport vessel being submersible from a level at which only a part of said lower pontoon lies below the water surface down to a level at which said lower pontoon lies entirely below and said deck construction entirely above the water surface, and down to a level at which said lower pontoon and said deck construction are situated entirely below the water level and only the upper part of at least one stabilizer box projecting above said deck construction projects above the water level.

2. Atransportvessel as claimed in claim 1, characterized in that the deck construction is constructed as a supporting surface for taking up a conventional transport pontoon and the stabilizer boxes projecting above the deck construction at the frontand/orthe rear of the transport vessel are spaced such a distance apart that a transport pontoon to betaken up can sail therebetween.

3. Atransportvesselasclaimedinclaim 1 or2, characterized in thatthe stabilizer boxes are situated at least partly at the front and the rear of the deck construction and the lower pontoon.

4. A submersibletransport vessel substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.